In a manufacturing process of a semiconductor device, a plasma etching process is repetitively performed to form a fine circuit pattern on a substrate such as a semiconductor wafer. In the plasma etching process, for example, plasma is generated by applying a high frequency voltage between facing electrodes in an evacuable processing chamber of a plasma processing apparatus. The plasma acts on the substrate mounted on a mounting table, and, thus, etching is carried out.
In order to perform a uniform and effective plasma process on a peripheral portion of the substrate as well as on a central portion thereof during the plasma etching process, a focus ring is provided on the mounting table so as to surround the substrate on the mounting table, and the etching is performed under such a configuration (see, for example, Patent Document 1).
In such a plasma processing apparatus, in order to perform a uniform and effective plasma process along a circumferential direction of the peripheral portion of the substrate, positioning holes are formed in a contact surface of the mounting table and the focus ring and then positioning pins are inserted into the positioning holes. In such a case, there is a need for increasing the insertion accuracy, i.e., narrowing a gap between the positioning holes and the positioning pins in a diametric direction when the focus ring is positioned. In this case, as the insertion accuracy improves, positioning accuracy of the focus ring can also be ameliorated.    Patent Document 1: Japanese Patent Laid-open Publication No. 2005-33062    Patent Document 2: Japanese Patent Laid-open Publication No. H10-265977
Since, however, the focus ring is exposed to the plasma of high temperature equal to or higher than several hundreds of degrees, a position deviation may be caused between the components such as the mounting table and the focus ring made of different materials due to a difference in thermal expansion amounts of these components. For the reason, as the insertion of the positioning pins into the position holes is increased, a greater force is applied to the positioning pins or the focus ring when the focus ring is deviated from the mounting table due to the difference in their thermal expansion amounts, resulting in damage on the positioning pins or the focus ring.
Conventionally, therefore, a heat resistant material (e.g., polyimide) hardly suffering thermal deformation under a high heat condition has been preferred as a material for the positioning pins. Further, it has been attempted to loosen the insertion accuracy of the positioning pins into the positioning holes in consideration of the thermal expansion of the mounting table or the focus ring.
However, as the insertion accuracy is loosened, the gap between the positioning holes and the positioning pins in the diametric direction increases, and, thus, there is a likelihood that the focus ring may be deviated from its original position. If the focus ring is deviated, a gap between an outer peripheral surface of the substrate and an inner peripheral surface of the focus ring may become non-uniform along a circumferential direction of the substrate. Thus, a substrate temperature may also become non-uniform along the circumferential direction of the peripheral portion of the substrate, resulting in a failure to maintain uniformity of the process.
As discussed above, components provided in the substrate processing apparatus are exposed to high heat of the plasma. Thus, when the positions of the components are aligned by inserting positioning pins into positioning holes, e.g., when the positions of other components such as an electrode plate of an upper electrode (see, for example, Patent Document 2) as well as the mounting table and the focus ring are aligned, there has been a limit in improving positioning accuracy between the components by increasing the insertion accuracy between the components.